The present invention relates to a projection optical apparatus, and more particularly to a front projector for magnifying and projecting an image on a reflection type display device onto a wall surface or a screen.
Conventional projectors have used a rotationally symmetric lens system. To obtain bright displays in this case, a reflection type display device such as a DMD (digital micro-mirror device or a reflection type LCD is used (see, for instance, JP-A 2000-98272).
Arrangements for illuminating a reflection type display device such as a PDLC or DMD through the whole or a part of a rotationally symmetric lens system have been proposed in JP-A""s 8-20175 and 8-251520.
For a head-mounted type image display system using a decentered prism, which is not a projection optical system, illumination by a reflection type LCD has been put forward in JP-A 11-337863, wherein illumination by the reflection type LCD is carried out through some reflecting surfaces and transmitting surfaces of the decentered prism.
In this regard, JP-A 2000-111800 discloses an image-formation optical system comprising two decentered prisms. In this image-formation optical system, a prism with an optical path crossing over itself therein is used as the prism located on the image plane side.
The present invention provides a projection optical
apparatus, comprising:
a reflection type display device,
a projection optical system for projecting an image displayed on the reflection type display device onto a projection display screen, and
an illumination light source for illuminating a display surface of the reflection type display device, wherein:
the projection optical system comprises an optical element having positive power,
said optical element being located in opposition to the display surface of the reflection type display device, and said optical element comprising at least two reflecting surfaces, at least one of which is defined by a rotationally asymmetric curved reflecting surface configured into a curved shape that imparts power to a light beam, and
the illumination light source is located such that given two light rays are reflected at at least first and second reflecting surfaces of the reflecting surfaces of the optical element as counted in order of a projection light ray traced from a display surface side, provided that said given two light rays are a light ray leaving the display surface and arriving at the projection display screen and a light ray leaving the illumination light source and arriving at the display surface,
said illumination light source being located such that an axis of illumination light incident on the optical element is not included in a given plane, wherein:
said axis of illumination light is defined by a center light ray of an illumination light beam from the illumination light source, said center light ray arriving at a center of the display surface,
an axis of projection light is defined by a light ray leaving the center of the display surface and arriving at the projection display screen through a center of a pupil of the optical system, and
said given plane is a plane that passes through the axis of projection light leaving the optical element and the center of the display surface.
The present invention also provides projection optical apparatus, comprising:
a reflection type display device,
a projection optical system for projecting an image displayed on the reflection type display device onto a projection display screen, and
an illumination light source for illuminating a display surface of the reflection type display device, wherein:
the projection optical system comprises an optical element having positive power,
said optical element being located in opposition to the display surface of the reflection type display device, and said optical element comprising at least two reflecting surfaces, at least one of which is defined by a rotationally asymmetric curved reflecting surface configured into a curved shape that imparts power to a light beam,
the illumination light source is located such that given two light rays are reflected at at least a first reflecting surface of the reflecting surfaces of the optical element as counted in order of a projection light ray traced from a display surface side, provided that said given two light rays are a light ray leaving the display surface and arriving at the projection display screen and a light ray leaving the illumination light source and arriving at the display surface,
said illumination light source being located such that an axis of illumination light incident on the optical element is not included in a given plane, wherein:
said axis of illumination light is defined by a center light ray of an illumination light beam from the illumination light source, said center light ray arriving at a center of the display surface,
an axis of projection light is defined by a light ray leaving the center of the display surface and arriving at the projection display screen through a center of a pupil of the optical system, and
said given plane is a plane that passes through the axis of projection light leaving the optical element and the center of the display surface, and the reflection type display device comprises a two-dimensionally arrayed micro-mirrors, each having a variable gradient so that an angle of emergence of reflected light can be varied.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of the parts, which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.